Postquam index inventus est, puella librum iterum evolvit, quia prooemium antea non legerat.

Because Latin often uses the perfect indicative after postquam to describe an action that was completed before the next one happened.

So postquam index inventus est literally has was found, but in natural English it may be best translated as after the index had been found. Latin does not always match English tense choices exactly here.

Inventus est is the perfect passive of invenio, invenire, inveni, inventus.

It is made of:

• inventus = the perfect passive participle, meaning found
• est = is/was, from sum

Together they mean was found or, depending on context, had been found.

Also, inventus is masculine singular, which shows that it agrees with index.

In a passive sentence, the thing receiving the action becomes the subject.

So in index inventus est, index is the subject, and inventus must agree with it in:

• gender
• number
• case

That is why you see inventus in the masculine singular nominative form.

Here index most likely means something like index, list, or table of contents, depending on the context of the passage.

A learner may be surprised because Latin index can have several meanings, such as:

• pointer
• sign
• informer
• index/list

The exact meaning depends on the context, but grammatically it is simply the subject of inventus est.

That is a very common question, because evolvit can look the same in writing as either:

• present: she unrolls / turns over
• perfect: she unrolled / turned over

You tell from the context. This sentence is clearly narrating past events:

• inventus est = a completed past action
• legerat = an even earlier past action

So evolvit is understood as perfect, meaning she opened / turned over / unrolled again.

Because librum is the direct object of evolvit.

The girl is doing the action of evolvit to the book, so Latin puts librum in the accusative singular.

Its dictionary form is liber, and:

• nominative singular: liber
• accusative singular: librum

The verb evolvo originally means roll out or unroll. From that basic idea, it can also mean things like:

• open
• turn over
• leaf through
• sometimes read through

With librum, the idea is probably that she opened the book again or turned through it again. The exact English wording depends on the style of translation.

Quia means because, so it introduces the reason for the main action.

Legerat is the pluperfect of lego, meaning had read. Latin uses the pluperfect here because her not reading the prooemium happened before she opened the book again.

So the time sequence is:

1. she had not read the preface earlier
2. therefore she opened the book again

It is not strictly necessary, but it adds emphasis and clarity.

Legerat already shows that the reading would have been earlier than the main action. Antea reinforces that idea by explicitly meaning earlier / before that / beforehand.

So Latin is being a little more explicit: she had previously not read the preface.

Prooemium means preface, introduction, or prologue.

It is a neuter second-declension noun. In neuter second-declension nouns, the nominative singular and accusative singular are the same, so:

• nominative: prooemium
• accusative: prooemium

Here it is accusative because it is the direct object of legerat.

Latin often leaves out subject pronouns when they are already clear.

In legerat, the verb ending already tells you the subject is he/she/it. Since puella was just named in the main clause, Latin does not need to repeat she.

So the subject of legerat is understood to be the same puella.

Latin word order is much more flexible than English word order because Latin uses endings to show grammatical function.

English depends heavily on position:

• the girl read the book is different from the book read the girl

Latin does not rely on order in the same way, because forms like puella, librum, and prooemium already show their roles. That lets Latin arrange words for emphasis or style.

In this sentence:

• Postquam index inventus est sets the time first
• puella librum iterum evolvit gives the main action
• quia prooemium antea non legerat gives the reason at the end

That ordering is very natural in Latin narrative.